Knowledge Centre · Guide · Pile integrity test and pile quality
Pile Integrity Test, CSL and Load Test: How to Check Pile Quality
A pile integrity test is a quick check that shows whether a finished pile has discontinuities along its length. However, it does not tell you how many tonnes the pile carries. In this guide we compare the pile integrity test with CSL and the load test, and explain which question each one answers.
Topic
Pile quality control
Reading time
About 7 minutes
Written by
Abdullah Çetintaş, Geological Engineer
Updated
November 2026
Testing by
Our testing partner
Example
Karaköy: PIT and coring
What is a pile integrity test, and how does it work?
PIT stands for pile integrity test; some people also call it a low-strain test. The technician strikes the pile head with a small hand hammer. The blow sends a wave down the pile, and the wave reflects back from changes in section and from the pile toe.
An accelerometer on the pile head records these reflections. Then an engineer interprets the signal: an unexpected reflection can point to a neck, a bulge or a discontinuity. Testing one pile takes a few minutes; for this reason, PIT often covers most of the piles on a site.
What does a pile integrity test show, and what does it not?
The strength of PIT is speed; its limit, on the other hand, is that it does not measure load. That is because a small blow does not load the ground; it only tells you about the geometry of the pile.
| Test | What it shows | What it does not show |
|---|---|---|
| Pile integrity test | Changes in section and signs of discontinuity along the pile | How many tonnes the pile carries |
| CSL (crosshole sonic logging) | The concrete between tubes fixed in advance | The zone outside the tubes in full |
| Static load test | Settlement under load and bearing capacity | The quality of the other piles on its own |
| Coring | The strength of jet grout and DSM columns | The condition of every column |
Limits: in very long piles or in high-friction ground the wave fades; as a result, the signal may not show the lower part of the pile clearly. That is why we always read PIT results together with the construction records.
What is CSL, and how does it differ from a pile integrity test?
In CSL, steel or plastic tubes go onto the reinforcement cage before concreting, and the concrete fills around them. During the test, a transmitter goes down one tube and a receiver down another; the instrument then measures the speed of the ultrasonic wave through the concrete between them.
CSL therefore shows the concrete inside the pile in more detail along its depth. On the other hand, you have to plan the tubes before construction; you cannot add them later. Also, it does not fully see the zone outside the tubes.
When do you need a static load test?
If you want to see how many tonnes a pile really carries, you need a load test. A hydraulic jack loads the pile in stages against a reaction beam, while gauges on an independent reference beam read the settlement.
This test needs preparation and time; for example, it needs reaction piles or kentledge. So it usually takes place on a few selected piles and goes into the programme from the start. When you need to confirm the design capacity, a PIT cannot replace it.
What to do before a pile integrity test
Whether the test gives a reliable result depends largely on preparation. For example, weak concrete at the top gives a false signal, and a sound pile can then look suspect.
- Waiting time: we wait until the concrete gains enough strength.
- Pile head: we break back the weak concrete at the top down to sound concrete.
- Cleaning: we level and clean the hammer and sensor points.
- Records: we keep each pile’s length, concrete volume and drilling record ready for the test.
- Interpretation: if a result looks suspect, we decide together with the designer.
On the office building in Karaköy, we had PIT carried out on the secant piles and cores taken from the jet grout columns. You can read the details on the Karaköy project page.
We also explain pile head trimming in a short video. However, the footage may be sample material for educational purposes.
You can find all our videos on our YouTube and Instagram accounts.
Frequently asked questions about the pile integrity test
We have collected the questions about pile testing that we hear most often. However, if yours is not here, call us or write through the quote form.
PIT and other tests
Is a pile integrity test mandatory?
The specification and the design decide that. Even so, many specifications include this test, and the client usually asks for it.
Who carries out the pile integrity test?
A specialist testing firm carries out the test; we work with our testing partner. Before the test, however, we prepare the pile heads ourselves.
How many piles need testing?
The specification sets the number. However, because the test is quick, it often covers most of the piles.
What happens if a pile integrity test gives a suspect result?
First, we check the construction records. If needed, we then arrange further tests, for example coring or a load test, and decide together with the designer.
Does a pile integrity test show bearing capacity?
No. A PIT only tells you about the continuity of the pile; for bearing capacity you need a static load test.
Sources
Talk to us about pile integrity tests and pile testing
Send us the specification and the pile schedule. Then let us agree the type, number and timing of the tests together with our partner.